A U.S. study, with input from Université de Montréal, finds surprisingly high particle emissions from cleaners, paints and perfumes – more than from cars and trucks.
Chemical products that contain compounds refined from petroleum – including household cleaners, pesticides, paints and perfumes – now rival motor vehicle emissions as the top source of urban air pollution, according to U.S. and Université de Montréal researchers.
People use a lot more fuel than they do petroleum-based compounds in chemical products – about 15 times more by weight, according to the new assessment published today in the journal Science by U.S. researchers and UdeM chemistry professor Patrick Hayes.
Even so, these products contribute about as much to air pollution as the transportation sector does, said lead author Brian McDonald, a University of Colorado researcher working with the U.S. National Oceanic and Atmospheric Administration (NOAA).
In the case of one type of pollution, tiny particles that can damage people’s lungs, emissions from chemical products are about twice as high as those from the transportation sector, McDonald's team found.
“As transportation gets cleaner, those other sources become more and more important,” said McDonald, an environmental engineer at the Cooperative Institute for Research in Environmental Sciences (CIRES), in Boulder. “The stuff we use in our everyday lives can impact air pollution.”
The same is true in Canada, added Hayes, who provided field measurements used in the study.
"We use the same chemical products and our motor vehicles and fuels are very similar to those in the U.S., so the study’s findings apply here as well," he said. "When we paint our houses or put on perfume, some of those products evaporate and form pollution particles in the atmosphere. Every year in Montreal there are dozens of days when the concentrations of particles in the air reach dangerous levels, especially for the most vulnerable, like the elderly or people who already suffer from respiratory disease."
Focus on volatile organic compounds
For the new assessment, the scientists focused on volatile organic compounds, or VOCs. VOCs can waft into the atmosphere and react to produce either ozone or particulate matter – both of which are regulated in the U.S., Canada and many other countries because of health impacts, including lung damage.
People living in cities and suburbs often assume that much of the pollution they breathe comes from car and truck emissions or leaky gas pumps. Though that was clearly true in past decades, regulators and car manufacturers have since made pollution-limiting changes to engines, fuels and pollution control systems.
In the new study, scientists reassessed air pollution sources by sorting through recent chemical production statistics compiled by U.S. industries and regulatory agencies, by making detailed atmospheric chemistry measurements in Los Angeles air, and by evaluating indoor air quality measurements made by others.
The scientists concluded that the amount of VOCs emitted by consumer and industrial products in the U.S. is actually two or three times greater than estimated by current air pollution inventories, which also overestimate vehicular sources. For example, the Environmental Protection Agency estimates that about 75 percent of VOC emissions (by weight) come from vehicular sources, and about 25 percent from chemical products. The new study, with its detailed assessment of up-to-date chemical use statistics and previously unavailable atmospheric data, puts the split closer to 50-50.
The disproportionate air-quality impact of chemical product emissions is partly due to a fundamental difference between those products and fuels, said NOAA atmospheric scientist Jessica Gilman, a co-author of the new paper. “Gasoline is stored in closed, hopefully airtight, containers and the VOCs in gasoline are burned for energy,” she said. “But volatile chemical products used in common solvents and personal care products are literally designed to evaporate. You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don't do this with gasoline."
Air pollution among top-5 threats to life
The researchers were particularly interested in how those VOCs end up contributing to particulate pollution. A comprehensive assessment published in the British medical journal Lancet last year put air pollution in a top-five list of global mortality threats, with “ambient particulate matter pollution” as the largest air pollution risk.
The new study finds that as cars have gotten cleaner, the VOCs forming those pollution particles are coming increasingly from consumer products.
“We’ve reached that transition point already in Los Angeles,” McDonald said.
He and his colleagues found that they simply could not reproduce the levels of particles or ozone measured in the atmosphere unless they included emissions from volatile chemical products. In the course of that work, they also determined that people are exposed to very high concentrations of volatile compounds indoors, which are more concentrated inside than out, said co-author Allen Goldstein, from the University of California Berkeley.
“Indoor concentrations are often 10 times higher indoors than outdoors, and that’s consistent with a scenario in which petroleum-based products used indoors provide a significant source to outdoor air in urban environments.”
The new assessment does find that the U.S. regulatory focus on car emissions has been very effective, said co-author Joost de Gouw, a CIRES chemist. “It’s worked so well that to make further progress on air quality, regulatory efforts would need to become more diverse. It’s not just vehicles anymore.”
About this study
“Volatile chemical products emerging as largest petrochemical source of urban organic emissions” was published Feb. 15, 2018 in the journal Science. Its authors are: Brian C. McDonald, Joost A. de Gouw, Stuart A. McKeen, Yu Yan Cui, Si-Wan Kim (University of Colorado – Boulder, Cooperative Institute for Research in Environmental Sciences, National Oceanic and Atmospheric Administration Chemical Sciences Division); Jessica B. Gilman (NOAA CSD); Shantanu H. Jathar (Colorado State University and University of California – Davis), Ali Akherati (Colorado State University), Christopher D. Cappa (University of California – Davis), Jose L. Jimenez (CIRES and University of Colorado – Boulder), Julia Lee-Taylor (CIRES and National Center for Atmospheric Research); Patrick L. Hayes (Université de Montréal); Drew R. Gentner (Yale University); Gabriel Isaacman (NCAR); VanWertz (Virginia Tech); Allen H. Goldstein, Robert A. Harley (University of California – Berkeley); Gregory J. Frost, James M. Roberts, Thomas B. Ryerson, Michael Trainer (NOAA CSD). The research was supported by NOAA, the CIRES Visiting Fellowship Program, Aerodyne Research, Inc, the National Science Foundation and the Sloan Foundation. CIRES is a partnership of NOAA and the University of Colorado – Boulder.
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